1. Field of the Invention
The present invention relates to a data processing apparatus, such as a personal computer, a word processor and a typewriter, with edit functions.
2. Description of Related Art
A conventional data processing apparatus, such as the personal computer, the word processor and the typewriter, with edit functions, for example, a small-size portable word processor known as a note type, or a book type, comprises a key board, a liquid crystal display and floppy disk drives. These parts are compactly arranged in a main body. In recent years, in the data processing apparatus of the type mentioned, a transmission type liquid crystal display with a back light is provided enabling an operator to-easily see the display on the liquid crystal display.
The above-mentioned small-size portable word processor can be operated on a commercial power supply with an AC adapter, and further, can be operated on batteries in place of the commercial power supply for a certain interval of time. Therefore, the word processor can be operated in any place without a commercial power supply. In the word processor comprising the above-mentioned liquid crystal display with the back light, the amount of electric power consumed is large when the back light is lit, more particularly, the amount of power consumed is very large when the back light is lit and simultaneously a floppy disk drive is driven. Therefore, in the conventional word processor, a power supply unit having a large-size and large-capacity is installed for dealing with the case when the back light is lit and simultaneously the floppy disk drive is driven.
Since the amount of electric power consumed is large when the back light is lit in the word processor, when key input operation is not executed in a predetermined interval of time, the back light is automatically turned off in order to save electric power in prior art devices. For example, this is proposed in Japanese Laid-Open Utility Model Publication No. 62-22630.
However, in this way, even if the back light is automatically turned off when key input operation is not executed in a predetermined interval of time, the amount of the electric power to be saved is small. Therefore, there is still a need to install a power supply unit having a large-size and large-capacity into the word processor in order to deal with the case that the back light is lit and simultaneously the floppy disk drive is driven.
Thus, in the conventional data processing apparatus having a liquid crystal display with the back light, a power supply unit having a large-size and large-capacity has to be installed. Therefore, the data processing apparatus can not be compact and lightweight, and the power supply unit is expensive.